Lift fork for stacking articles



Sept. 20, 1960 E. HALL ET AL 2,953,269

LIFT RoRR FOR sTAcxING ARTICLES 2 Sheets-Sheet 1 Filed Aprl ll, 1958'ATTORNEYS Sept. 20, 1960 E. HALL ET AL 1.1m" FORK FOR sTAcKING ARTICLES2 Sheets-Sheet 2 Filed April 1l, 1958 INVENT i taes LFT FORK FORSTACKING ARTICLES Filed Apr. 11, 1958, Ser. No. 727,909

4 Claims. (Cl. 214-653) The present invention relates to lift forks usedf or lifting and transporting loads of articles, each load consisting ofa multiplicity of articles such as filled cartons or boxes, stacked orarranged in a compact pile or group, and more particularly toimprovements on a lift fork of the general type shown and described inPatent No. 2,530,375, issued to V. H. Cartwright. In this patent thereis disclosed a lift fork comprising a pair of vertical parallelrelatively movable frames, one of which is constructed to be attachedtopa lift fork truck or vehicle equipped with means for raising andlowering the frame, and the `other ofwhich carries horizontallyextending tines adapted to engage theload. These tines are equipped withlaterally operable and opposed gripper devices which `are expansible orretractable to grip articles at the lower courses of the load and liftthem -together with the remaining upper portion of the load. The upperportion of the load is supported by the top surface ofv these tines,principally, and to some extent may receive some support from thegripped articles in the lower courses of the load.

The present invention, in the preferred form herein illustrated,provides an efiicient means for expanding and contracting the grippermeans under the positive control of the lift fork operator so that thearticles in the lower portion of the load, when lying between the tinesof the fork, may be gripped for lifting independently of action of thelift fork on the upper portion of the load, this being one of theobjects attained by the invention.

Another object of the invention is to provide 4a lift fork apparatuswhich will handle from one article to a full load of articles, therebyeliminating the prior practice of handling partial loads manually.

Another object of the invention is to provide independently controlledfluid actuated means for expanding and contracting the gripper devicescarried by the tines, their gripping force being regulable, whengripping articles to lift them, not to exceed a gripping force that willcause damage to the articles.

Another object of the invention is -to provide a lift fork apparatushaving the foregoing advantages that is easily and economicallyconstructed and maintained.

Another object of the invention is to provide individual fluid-actuatedmotors that are remotely controlled for operation in unison forexpanding and contracting the gripper devices on each of the tines for,at will, gripping and releasing articles put between the tines.

Other objects and advantages of the present invention will becomeapparent from a reading of the following description of a preferredembodiment, the appended claims, and the accompanying drawings of thepreferred embodiment to which reference is made and in which:

Fig. 1 is a three-quarter front perspective view of the lift fork of theapparatus, a portion of a lift truck or vehicle appearing in phantomview.

Fig. 2 is a rear elevational view of the lift fork frame taken alongline 2-2 of Fig. y1.

Fig. 3 is a partially diagrammatic view, showing the fluid system andcontrols for actuation of the iluid operating motors drivably connectedto expand or contract one of the gripper devices.

Fig. 4 is a sectional view of the control valve of the system formanually controlling operation of the motors.

Referring to Fig. l, which illustrates the lift fork apparatus, theapparatus includes a supporting frame 10 which is movably attached to alifting frame 11 mounted at the front of a truck or vehicle 12, saidlifting frame being power operated for lifting and lowering the fork.The supporting frame 10 has a vertical wall frame 13 attached theretoand in spaced relationship. The vertical wall frame 13 has a pluralityof 4tines 14 depending horizontally from the lower portion 13a of thewall frame. The tines 14 extend horizontally forward and are spacedapart in parallel relationship, one to the other, the spacingstherebetween being substantially equal. Any desired number including atleast two tines 14 may be built into the structure. The outermost or endtines 14 are provided with a single set of gripper bars 15, on theirinside vertical faces and the intermediate tines between the end tinesare provided with two sets of gripper bars 15 on both inside verticalfaces. The gripper bars 15 are arranged to `oppose complementary gripperbars on the adjacent tine 14 and are movable laterally with `respect tothe tines by expanding and retracting movement to engage an articleplaced between the tines. The gripper bars 15 rare mounted for movementsimilar to that disclosed in the Cartwright patent, No. 2,530,375, andare actuated in expanding and retracting movement by reciprocatingmovement of longitudinal linkage members 16 (Fig. 3) slidable withineach tine 1-4.

As seen in Fig. 3, each Iof the longitudinal members 16 is pin connectedto a pivotal crank 17 by pin 18, the crank 17 being pivoted on a bracket19` integral at the back side of the lower portion 13a of the wall frame13. This crank connection is provided ttor reciprocal action of eachlongitudinal member 16 in tines 14. Fluid-operated motors 21 -areprovided to drive each member 16, the motors being in the form ofcylinderpiston assemblies, which comprise a cylinder 22 with 0ppositeend ports 23 and 24 for the admission of pressure lluid to move itsinternal piston in either direction. The piston (not shown) carries aconnecting rod 25 having an end block 26 and is pivotally connectedthereby at its outer end to the free end of the corresponding crank 17by a pin 27 extending through one of the series of holes 28 in block 26.This lseries of holes 28 permits a stroke adjustment for each of themotors 21. As indicated on Fig. 2, the outermost motors may be ofsmaller size than the motors located inwardly therefrom, since these-outermost motors are required to drive but one set of the gripper bars15 at the innerfacing on each of the outermost or end tines. The tineslocated intermediate these two end tines each have a double set ofgripper bars facing in opposite `directions on their vertical facings,hence, the motor for driving them is preferably of a correspondinglylarger size. In any event, each of the mot-ors 21 are lmounted similarlyyand operate in the same manner and in unison, as will be presentlydescribed. Each cylinder 22 of the two outermost motors have an upperend lug 29 pin connected at pin 30` to bracket 31 projecting rearwardlyon lower wall frame 13a. The centrally disposed motor 21 has a similarpin connection on crossbar 32 across the uprights of wall frame 13.Thus, the cylinders of the motors 21 are each held on the wall frame ofthe lift fork.

As seen from Figs. 2 and 3, each of the motors are connected into apressure uid system for activating the motors in either direction. Inthis connection, the system herein illustrated is provided for operatingdoubleacting cylinder assemblies, however, it should be obvious thatsingle-acting cylinder piston assemblies would operate just as well if,as will be seen from the following description of the system fordouble-acting cylinders, the movement of the motor for releasing thegripperdevices is powered by a spring biasing the power or positivestroke of the cylinder.

From Fig. 3, we see that a sump and pump unit 33 supplies a continuoussource of uid under pressure into a conduit 34. Conduit 34 is connectedin series with a conventional variable pressure regulator 35 that isadjustable for regulating the pressure of the iluid being supplied fromthe pump. At the outlet side of the pressure regulator is a conduitconnection 36 to the inlet port 37 of a manually-operated control valve,referred to generally as 38. A pressure gauge 39 may be interposed inconduit 36 to'indicate a measurement of the pressure of the fluid thatis being supp-lied by the pump through the pressure regulator 35. As maybe seen from Fig. 4, with occasional cross-reference to Fig. 3, thecontrol valve 38 has an axial shiftable valve spool 40 having threeannular lands 4l, 42, and 43 thereon. The central shaft 44 of the valvespool 40 extends outwardly of the body of the Valve 38-and is sealedagainst leakage by a gland 45. The outer end of shaft 44 has a pivotalconnection to the lower end of control lever 46 at a yoke 47 pinnedthrough a bearing 44a on shaft 44. The lever 46 is mounted on a pivot 48journaled on a bracket 49 which is part of the vehicle l2. Lever 46 isshiftable between the extreme settings- A (solid outline) and B (dottedoutline) and is capable of being set in an intermediate position C. Thepumpl and sump unit 33 is preferably mounted on the truck l2 of the liftfork apparatus and driven by power take-olf connection (not shown) fromthe vehicle l2. The control valve 38 and lever 46 may be convenientlymounted on the Vehicle l2 for ready access to these controls by the liftfork operator.

The control valve 38 'has ports 5.0 and 51 connected by uid conduits 52and 53, respectively, which extend to respective connectionson a rstheader 54 and a second header 55. These rst and second headers 54 and 55are fastened transversely of the vertical uprights at the back of thewall frame i3. The first header 54-has Huid connections by conduits 56to the upper port 23 of each of the cylinders 22 of the motors. Thesecond header 55 has fluid connections by conduits 57 to the lower port24v of each cylinder 22 of the motors. The Valve 38 also has upperexhaust ports 58 7and 59 connected, respectively, by iiuid connectionsat conduits 60 and 61 leading to the sump of the pump-sump unit 33.

Hence, as the control lever`46 is set in the position A (sho-wn in solidoutline), fluid from the pump enters the valve 3S at port 37 and isconducted between lands 42 and 43 of the valve spool 40 to the port 5iand into the irst header 54 through conduit 53. The pressure fluidpresent in the rst header is then conducted through the three conduits56 into the upper ports 23 of the three cylinders 22 of the motorsforcing their pistons downwardly to extend the connecting rod 25. Fluidbelow the pistons is permitted to exhaust out ports 24, conduits S7 andiiow tol second header S5., thence through conduit 52, valve port Sti,exhaust port 55, conduit 66, and to the sump of pump-sump unit 33. Thispermits driving motionv by the motors to rotate the three cranks 17counterclockwise about their pivots 20 to drive the longitudinal linkagemembers )i6 longitudinally into the tines and force the gripper bars ito expand against an article placed between the tines. By setting thepressure regulator 35 of this system to a fluid pressure correspondingto a driving force of the motor that is slightly. in excess of the forcenecessary to grip and lift articles engaged by the gripper bars willprovide a satisfactory means for handling these articles without causingdamage thereto by, excessive compressive forces upon gripping them, rJhecontrol lever 46 may also be set in its intermediate position C in whichevent the valve spool lands 41, 42, and 43, respectively, will blockports 53, 3'7, and 59 of the valve and lock the gripper bars on thetines in gripping engagement on the articles.

To release gripped articles, the control lever may be shifted to theindicated position B, in which event the valve spool 4t) will connectfluid pressure entering at inlet port 37 to port 50 and conduct uidpressure through conduit 52 to the second header S5. The pressure thenin header S5 will be distributed through conduits 5'7; to enter thecylinders 22 of the three motors through their lower ports 24 `andactuate their pistons upwardly. Fluid above the pistons of cylinders 22is exhausted through ports 23, conduits 56|, iirst header 54, conduit53, port 5l, exhaust port 59, and conduit 61 to the sump. This movementwill drive the crank 17 in a clockwise direction about theirV pins 20and withdraw the longitudinal linkage member 16 in the tines 14causing'the gripper bars 15 to retract and release the articles.

Various modications may be resorted to within the spirit and scope ofthe appended claims.

We claim:

1. In `a lift fork apparatus for carrying articles provided with a frameadapted tobe mounted for Vertical movement on a vehicle and including aplurality of parallel members attached to depend horizontally from saidframe and'having equal spacing therebetween to receive articles, andopposed article gripper means movable on said members in cooperatingrelationship to act on articles received between said members when movedin one direction and to release the articles when moved in the otherdirection, in combination therewith, a longitudinally disposed linkagealong each said member and operable by reciprocating movement to movesaid gripper means -inreither direction, a crank arm operativelyconnected to each said linkage and pivotally mounted on the frame,fluid-operated reciprocating motors for driving said linkagesindividually through pivotal connection of the connecting rod thereof onsaid crank arm, the cylinder of said motor being held on the frame,opposite end ports in the cylinder of each said motor, a rst fluidheader, uid conduits connecting said iirst header to one end port ofeach said cylinder, a second fluid header, Huid conduits connecting saidsecond headerto the. other. end port of each said cylinder, a fluidpressure source, a sump, a hand-operated control valve, fluid conduitsconnecting the control valve respectively to the source, first header,second header and the sump, said control valve being adapted forsettings alternatively to: (l) connect the rst header andthe source andthe second header and the sump and cause pressure iuid to actuate eachof the motors to move their said linkage and gripper means in thedirection to act on articles between said members, and (2) connect thesecond header and the source and the iirst header and the sump and causepressure fluid to actuate each of the motors to move their linkage andgripper means in the direction to release said article.

2. The combination defined in claim 1, wherein the said control valveincludes an alternative hold setting, said setting blocking therespective connections between both said first and second headers.`andthe pump and the sump, whereby the motors lock the article grippingmeans against movement in either direction.

3. The combination deiined in claim 1, characterized by including -aVariable pressure regulating meansin. the iluid conduit between thefirst header andthe source, thereby to permit regulation of the pressureactuating force of the motors in moving the gripper means in thedirection to act on `a given kind of articles of' slightly more than thegripping force necessary to lift one ofsaid articles and prevent damagethereto upon gripping same.

4. The combination defined in claim 3, including, in .operative seriesconnection in said fluid conduit with the 5 variable pressure regulatingmeans, a pressure gauge in- 2,571,550 dioating the amount of ud pressurebeing delivered to 2,771,204 said rst header.

References Cited in the file of this patent 5 132 666 UNITED STATESPATENTS 2,530,375 Cartwright NOV. 21, 1950 6 Ehmann Oct. 16, 1951McCormick Nov. 20, 1956 FOREIGN PATENTS Australia May 18, 1949

